And here's another of those old Javanese ladrang form similar to yours. I also throw in a Sulawesi sheath, which if you look carefully, has the similar 'leave' structures on both ends of the sheath, but a lot more subdued. The boxy form is clearly evident in both sheaths.

Now it's not so difficult to visualize the commonality between the Javanese keris and the Bugis keris, is it.